Sea temperatures dropped as much as 12.6 degrees Fahrenheit (7 degrees Celsius) after the Chicxulub crater blast blanketed the planet in ashy darkness, halting photosynthesis, concludes the team led Johan Vellekoop of Utrecht University in the Netherlands.

Long suspected and now confirmed, the long-ago global winter has been seen as playing a major role in the mass extinction that followed the asteroid's impact in what is today Mexico's Yucatan. All dinosaurs—with the exception of birds—along with many marine reptiles and plant species, disappeared in the ancient calamity.

Volcanoes, wildfires, and tsunamis also added to the impact's deadly effects, with the catastrophe playing out over a century, according to the analysis.